feat(usb): add support for ISO endpoints

1 files changed, 186 insertions, 25 deletions

diff --git a/embassy-stm32/src/usb/usb.rs b/embassy-stm32/src/usb/usb.rs
index 9384c8688..0ab2306c8 100644
--- a/embassy-stm32/src/usb/usb.rs
+++ b/embassy-stm32/src/usb/usb.rs
@@ -80,6 +80,8 @@ impl<T: Instance> interrupt::typelevel::Handler<T::Interrupt> for InterruptHandl
 
         if istr.ctr() {
             let index = istr.ep_id() as usize;
+            CTR_TRIGGERED[index].store(true, Ordering::Relaxed);
+
             let mut epr = regs.epr(index).read();
             if epr.ctr_rx() {
                 if index == 0 && epr.setup() {
@@ -120,6 +122,10 @@ const USBRAM_ALIGN: usize = 4;
 const NEW_AW: AtomicWaker = AtomicWaker::new();
 static BUS_WAKER: AtomicWaker = NEW_AW;
 static EP0_SETUP: AtomicBool = AtomicBool::new(false);
+
+const NEW_CTR_TRIGGERED: AtomicBool = AtomicBool::new(false);
+static CTR_TRIGGERED: [AtomicBool; EP_COUNT] = [NEW_CTR_TRIGGERED; EP_COUNT];
+
 static EP_IN_WAKERS: [AtomicWaker; EP_COUNT] = [NEW_AW; EP_COUNT];
 static EP_OUT_WAKERS: [AtomicWaker; EP_COUNT] = [NEW_AW; EP_COUNT];
 static IRQ_RESET: AtomicBool = AtomicBool::new(false);
@@ -163,20 +169,37 @@ fn calc_out_len(len: u16) -> (u16, u16) {
 mod btable {
     use super::*;
 
-    pub(super) fn write_in<T: Instance>(index: usize, addr: u16) {
+    pub(super) fn write_in_tx<T: Instance>(index: usize, addr: u16) {
         USBRAM.mem(index * 4 + 0).write_value(addr);
     }
 
-    pub(super) fn write_in_len<T: Instance>(index: usize, _addr: u16, len: u16) {
+    pub(super) fn write_in_rx<T: Instance>(index: usize, addr: u16) {
+        USBRAM.mem(index * 4 + 2).write_value(addr);
+    }
+
+    pub(super) fn write_in_len_rx<T: Instance>(index: usize, _addr: u16, len: u16) {
+        USBRAM.mem(index * 4 + 3).write_value(len);
+    }
+
+    pub(super) fn write_in_len_tx<T: Instance>(index: usize, _addr: u16, len: u16) {
         USBRAM.mem(index * 4 + 1).write_value(len);
     }
 
-    pub(super) fn write_out<T: Instance>(index: usize, addr: u16, max_len_bits: u16) {
+    pub(super) fn write_out_rx<T: Instance>(index: usize, addr: u16, max_len_bits: u16) {
         USBRAM.mem(index * 4 + 2).write_value(addr);
         USBRAM.mem(index * 4 + 3).write_value(max_len_bits);
     }
 
-    pub(super) fn read_out_len<T: Instance>(index: usize) -> u16 {
+    pub(super) fn write_out_tx<T: Instance>(index: usize, addr: u16, max_len_bits: u16) {
+        USBRAM.mem(index * 4 + 0).write_value(addr);
+        USBRAM.mem(index * 4 + 1).write_value(max_len_bits);
+    }
+
+    pub(super) fn read_out_len_tx<T: Instance>(index: usize) -> u16 {
+        USBRAM.mem(index * 4 + 1).read()
+    }
+
+    pub(super) fn read_out_len_rx<T: Instance>(index: usize) -> u16 {
         USBRAM.mem(index * 4 + 3).read()
     }
 }
@@ -184,19 +207,37 @@ mod btable {
 mod btable {
     use super::*;
 
-    pub(super) fn write_in<T: Instance>(_index: usize, _addr: u16) {}
+    pub(super) fn write_in_tx<T: Instance>(_index: usize, _addr: u16) {}
 
-    pub(super) fn write_in_len<T: Instance>(index: usize, addr: u16, len: u16) {
+    pub(super) fn write_in_rx<T: Instance>(_index: usize, _addr: u16) {}
+
+    pub(super) fn write_in_len_tx<T: Instance>(index: usize, addr: u16, len: u16) {
         USBRAM.mem(index * 2).write_value((addr as u32) | ((len as u32) << 16));
     }
 
-    pub(super) fn write_out<T: Instance>(index: usize, addr: u16, max_len_bits: u16) {
+    pub(super) fn write_in_len_rx<T: Instance>(index: usize, addr: u16, len: u16) {
+        USBRAM
+            .mem(index * 2 + 1)
+            .write_value((addr as u32) | ((len as u32) << 16));
+    }
+
+    pub(super) fn write_out_tx<T: Instance>(index: usize, addr: u16, max_len_bits: u16) {
+        USBRAM
+            .mem(index * 2)
+            .write_value((addr as u32) | ((max_len_bits as u32) << 16));
+    }
+
+    pub(super) fn write_out_rx<T: Instance>(index: usize, addr: u16, max_len_bits: u16) {
         USBRAM
             .mem(index * 2 + 1)
             .write_value((addr as u32) | ((max_len_bits as u32) << 16));
     }
 
-    pub(super) fn read_out_len<T: Instance>(index: usize) -> u16 {
+    pub(super) fn read_out_len_tx<T: Instance>(index: usize) -> u16 {
+        (USBRAM.mem(index * 2).read() >> 16) as u16
+    }
+
+    pub(super) fn read_out_len_rx<T: Instance>(index: usize) -> u16 {
         (USBRAM.mem(index * 2 + 1).read() >> 16) as u16
     }
 }
@@ -327,6 +368,13 @@ impl<'d, T: Instance> Driver<'d, T> {
                 return false; // reserved for control pipe
             }
             let used = ep.used_out || ep.used_in;
+            if used && (ep.ep_type == EndpointType::Isochronous || ep.ep_type == EndpointType::Bulk) {
+                // Isochronous and bulk endpoints are double-buffered.
+                // Their corresponding endpoint/channel registers are forced to be unidirectional.
+                // Do not reuse this index.
+                return false;
+            }
+
             let used_dir = match D::dir() {
                 Direction::Out => ep.used_out,
                 Direction::In => ep.used_in,
@@ -350,7 +398,11 @@ impl<'d, T: Instance> Driver<'d, T> {
                 let addr = self.alloc_ep_mem(len);
 
                 trace!("  len_bits = {:04x}", len_bits);
-                btable::write_out::<T>(index, addr, len_bits);
+                btable::write_out_rx::<T>(index, addr, len_bits);
+
+                if ep_type == EndpointType::Isochronous {
+                    btable::write_out_tx::<T>(index, addr, len_bits);
+                }
 
                 EndpointBuffer {
                     addr,
@@ -366,7 +418,11 @@ impl<'d, T: Instance> Driver<'d, T> {
                 let addr = self.alloc_ep_mem(len);
 
                 // ep_in_len is written when actually TXing packets.
-                btable::write_in::<T>(index, addr);
+                btable::write_in_tx::<T>(index, addr);
+
+                if ep_type == EndpointType::Isochronous {
+                    btable::write_in_rx::<T>(index, addr);
+                }
 
                 EndpointBuffer {
                     addr,
@@ -656,6 +712,18 @@ impl Dir for Out {
     }
 }
 
+/// Selects the packet buffer.
+///
+/// For double-buffered endpoints, both the `Rx` and `Tx` buffer from a channel are used for the same
+/// direction of transfer. This is opposed to single-buffered endpoints, where one channel can serve
+/// two directions at the same time.
+enum PacketBuffer {
+    /// The RX buffer - must be used for single-buffered OUT endpoints
+    Rx,
+    /// The TX buffer - must be used for single-buffered IN endpoints
+    Tx,
+}
+
 /// USB endpoint.
 pub struct Endpoint<'d, T: Instance, D> {
     _phantom: PhantomData<(&'d mut T, D)>,
@@ -664,15 +732,46 @@ pub struct Endpoint<'d, T: Instance, D> {
 }
 
 impl<'d, T: Instance, D> Endpoint<'d, T, D> {
-    fn write_data(&mut self, buf: &[u8]) {
+    /// Write to a double-buffered endpoint.
+    ///
+    /// For double-buffered endpoints, the data buffers overlap, but we still need to write to the right counter field.
+    /// The DTOG_TX bit indicates the buffer that is currently in use by the USB peripheral, that is, the buffer in
+    /// which the next transmit packet will be stored, so we need to write the counter of the OTHER buffer, which is
+    /// where the last transmitted packet was stored.
+    fn write_data_double_buffered(&mut self, buf: &[u8], packet_buffer: PacketBuffer) {
         let index = self.info.addr.index();
         self.buf.write(buf);
-        btable::write_in_len::<T>(index, self.buf.addr, buf.len() as _);
+
+        match packet_buffer {
+            PacketBuffer::Rx => btable::write_in_len_rx::<T>(index, self.buf.addr, buf.len() as _),
+            PacketBuffer::Tx => btable::write_in_len_tx::<T>(index, self.buf.addr, buf.len() as _),
+        }
     }
 
-    fn read_data(&mut self, buf: &mut [u8]) -> Result<usize, EndpointError> {
+    /// Write to a single-buffered endpoint.
+    fn write_data(&mut self, buf: &[u8]) {
+        self.write_data_double_buffered(buf, PacketBuffer::Tx);
+    }
+
+    /// Read from a double-buffered endpoint.
+    ///
+    /// For double-buffered endpoints, the data buffers overlap, but we still need to read from the right counter field.
+    /// The DTOG_RX bit indicates the buffer that is currently in use by the USB peripheral, that is, the buffer in
+    /// which the next received packet will be stored, so we need to read the counter of the OTHER buffer, which is
+    /// where the last received packet was stored.
+    fn read_data_double_buffered(
+        &mut self,
+        buf: &mut [u8],
+        packet_buffer: PacketBuffer,
+    ) -> Result<usize, EndpointError> {
         let index = self.info.addr.index();
-        let rx_len = btable::read_out_len::<T>(index) as usize & 0x3FF;
+
+        let rx_len = match packet_buffer {
+            PacketBuffer::Rx => btable::read_out_len_rx::<T>(index),
+            PacketBuffer::Tx => btable::read_out_len_tx::<T>(index),
+        } as usize
+            & 0x3FF;
+
         trace!("READ DONE, rx_len = {}", rx_len);
         if rx_len > buf.len() {
             return Err(EndpointError::BufferOverflow);
@@ -680,6 +779,11 @@ impl<'d, T: Instance, D> Endpoint<'d, T, D> {
         self.buf.read(&mut buf[..rx_len]);
         Ok(rx_len)
     }
+
+    /// Read from a single-buffered endpoint.
+    fn read_data(&mut self, buf: &mut [u8]) -> Result<usize, EndpointError> {
+        self.read_data_double_buffered(buf, PacketBuffer::Rx)
+    }
 }
 
 impl<'d, T: Instance> driver::Endpoint for Endpoint<'d, T, In> {
@@ -734,25 +838,53 @@ impl<'d, T: Instance> driver::EndpointOut for Endpoint<'d, T, Out> {
             EP_OUT_WAKERS[index].register(cx.waker());
             let regs = T::regs();
             let stat = regs.epr(index).read().stat_rx();
-            if matches!(stat, Stat::NAK | Stat::DISABLED) {
-                Poll::Ready(stat)
+            if self.info.ep_type == EndpointType::Isochronous {
+                // The isochronous endpoint does not change its `STAT_RX` field to `NAK` when receiving a packet.
+                // Therefore, this instead waits until the `CTR` interrupt was triggered.
+                if matches!(stat, Stat::DISABLED) || CTR_TRIGGERED[index].load(Ordering::Relaxed) {
+                    Poll::Ready(stat)
+                } else {
+                    Poll::Pending
+                }
             } else {
-                Poll::Pending
+                if matches!(stat, Stat::NAK | Stat::DISABLED) {
+                    Poll::Ready(stat)
+                } else {
+                    Poll::Pending
+                }
             }
         })
         .await;
 
+        CTR_TRIGGERED[index].store(false, Ordering::Relaxed);
+
         if stat == Stat::DISABLED {
             return Err(EndpointError::Disabled);
         }
 
-        let rx_len = self.read_data(buf)?;
-
         let regs = T::regs();
+
+        let packet_buffer = if self.info.ep_type == EndpointType::Isochronous {
+            // Find the buffer, which is currently in use. Read from the OTHER buffer.
+            if regs.epr(index).read().dtog_rx() {
+                PacketBuffer::Rx
+            } else {
+                PacketBuffer::Tx
+            }
+        } else {
+            PacketBuffer::Rx
+        };
+
+        let rx_len = self.read_data_double_buffered(buf, packet_buffer)?;
+
         regs.epr(index).write(|w| {
             w.set_ep_type(convert_type(self.info.ep_type));
             w.set_ea(self.info.addr.index() as _);
-            w.set_stat_rx(Stat::from_bits(Stat::NAK.to_bits() ^ Stat::VALID.to_bits()));
+            if self.info.ep_type == EndpointType::Isochronous {
+                w.set_stat_rx(Stat::from_bits(0)); // STAT_RX remains `VALID`.
+            } else {
+                w.set_stat_rx(Stat::from_bits(Stat::NAK.to_bits() ^ Stat::VALID.to_bits()));
+            }
             w.set_stat_tx(Stat::from_bits(0));
             w.set_ctr_rx(true); // don't clear
             w.set_ctr_tx(true); // don't clear
@@ -776,25 +908,54 @@ impl<'d, T: Instance> driver::EndpointIn for Endpoint<'d, T, In> {
             EP_IN_WAKERS[index].register(cx.waker());
             let regs = T::regs();
             let stat = regs.epr(index).read().stat_tx();
-            if matches!(stat, Stat::NAK | Stat::DISABLED) {
-                Poll::Ready(stat)
+            if self.info.ep_type == EndpointType::Isochronous {
+                // The isochronous endpoint does not change its `STAT_RX` field to `NAK` when receiving a packet.
+                // Therefore, this instead waits until the `CTR` interrupt was triggered.
+                if matches!(stat, Stat::DISABLED) || CTR_TRIGGERED[index].load(Ordering::Relaxed) {
+                    Poll::Ready(stat)
+                } else {
+                    Poll::Pending
+                }
             } else {
-                Poll::Pending
+                if matches!(stat, Stat::NAK | Stat::DISABLED) {
+                    Poll::Ready(stat)
+                } else {
+                    Poll::Pending
+                }
             }
         })
         .await;
 
+        CTR_TRIGGERED[index].store(false, Ordering::Relaxed);
+
         if stat == Stat::DISABLED {
             return Err(EndpointError::Disabled);
         }
 
-        self.write_data(buf);
+        let regs = T::regs();
+
+        let packet_buffer = if self.info.ep_type == EndpointType::Isochronous {
+            // Find the buffer, which is currently in use. Write to the OTHER buffer.
+            if regs.epr(index).read().dtog_tx() {
+                PacketBuffer::Tx
+            } else {
+                PacketBuffer::Rx
+            }
+        } else {
+            PacketBuffer::Tx
+        };
+
+        self.write_data_double_buffered(buf, packet_buffer);
 
         let regs = T::regs();
         regs.epr(index).write(|w| {
             w.set_ep_type(convert_type(self.info.ep_type));
             w.set_ea(self.info.addr.index() as _);
-            w.set_stat_tx(Stat::from_bits(Stat::NAK.to_bits() ^ Stat::VALID.to_bits()));
+            if self.info.ep_type == EndpointType::Isochronous {
+                w.set_stat_tx(Stat::from_bits(0)); // STAT_TX remains `VALID`.
+            } else {
+                w.set_stat_tx(Stat::from_bits(Stat::NAK.to_bits() ^ Stat::VALID.to_bits()));
+            }
             w.set_stat_rx(Stat::from_bits(0));
             w.set_ctr_rx(true); // don't clear
             w.set_ctr_tx(true); // don't clear